1. Field of the Invention
The present invention relates to a vehicular collision detection apparatus for a vehicle, which apparatus detects an object colliding with the vehicle, and which apparatus determines a category of the collision object.
2. Description of Related Art
Conventionally, apparatuses that detect collision of a vehicle with an object are described in, for example, JP-A-2005-538881 corresponding to US 2005/0116817 and JP-A-2006-117157 corresponding to US 2006/0087417. JP-A-2005-538881 describes a front sensor for a vehicle, which sensor has a sensing element in a cavity of the sensor. The front sensor uses the sensing element to detect the collision depending on deformation of the cavity. Also, JP-A-2006-117157 describes an apparatus that determines whether a collision object is a pedestrian based on change of pressure in the chamber space air-tightly formed between a bumper cover and a bumper reinforcement.
In general, a front end portion of the vehicle has a curved shape. In contrast, a front surface of a general bumper reinforcement has a shape that is not in parallel with the front end portion, but that is straight in a transverse direction of the vehicle. As a result, a chamber space defined between the bumper reinforcement and the front end portion (i.e., a bumper cover) has a length in the vehicle fore-and-aft direction, which length is changeable or different with a position in the vehicle transverse direction. Thus, the chamber forming member, which includes the chamber space, has a rigidity in the vehicle fore-and-aft direction changeable with a position in the vehicle transverse direction.
Also, a bumper absorber is disposed between the bumper cover and the bumper reinforcement in order to protect a leg of a pedestrian in a case, where the pedestrian collides with the bumper cover. In the above case, it is required that the bumper absorber be deformed but that the bumper cover be limited from contacting or being pressed against the bumper reinforcement. As above, the length of the chamber space in the vehicle fore-and-aft direction at end sections in the vehicle transverse direction is comparatively smaller relative to the fore-and-aft direction length of the chamber space at the center section of the chamber space. Thus, if rigidity of the bumper absorber or the chamber forming member is uniform in the vehicle transverse direction, the bumper cover may disadvantageously contact the bumper reinforcement in a case, where the pedestrian collides with the vehicle transverse direction end section. The above also applies to a case, where the chamber forming member serves as a bumper absorber.
Thus, in order to limit the bumper cover from contacting the bumper reinforcement even in a case, where a pedestrian collides with the bumper cover, the bumper absorber provided between the bumper cover and the bumper reinforcement has a variable rigidity in the vehicle fore-and-aft direction. In the above configuration, the variable rigidity is variably set based on the length of the chamber space in the vehicle fore-and-aft direction. Thus, the deformation amount of the chamber forming member varies depending on a position, at which the pedestrian collides with the bumper cover. As a result, disadvantageously, it has been difficult to highly accurately determine that the object, which collides with the bumper cover, is a pedestrian.